[Ivan_1966]

Maybe you could attach the steel bar that goes onto the open side before de-molding, to reinforce it?

Very good idea ! Yes, it will reinforcement the shape when flipping and de-casting the base (the face of X base).

Thank you !

[Ivan_1966]

Ordinary rotary(drum) mixers are not suitable for UHPC concrete. Especially if micro fibers are used. I removed the paddles from my mixer. I hastily welded a stand for double hand mixer from some profiles. I'm going to put some paddles inside in the mixer to grab the concrete which don't get in the way of the hand mixer. Both mixers will spin together. I hope to cast the X mold on Saturday.

P.S. That's better. With 2 such blades.

[Ivan_1966]

And today's optimization.

[Ivan_1966]

Leveling table for casting to 0.15 mm with various pads under a granite table. This is just rough leveling. Then, during the installation of X rails, there will be a fine leveling with an precise level indicator.

[Ivan_1966]

If anyone is interested.
3 days ago I made concrete samples with several different concrete mold releases. These are the results.
The liquid paraffin is applied very evenly, without drops. Backstein Plopp forms drops when applied.
But both release the form from the concrete very well.

[peteeng]

Hi Ivan - The 3 oil based products should release well. Plopp is an acid based release. It reacts with calcium in the concrete to form a soap at the wet concrete surface which then acts as the release. I have always used paste wax (Cornubia wax based) such as attached. Liquid releases can drain down vertical surfaces and pond at the bottom. Plus wax can be buffed to a high polish finish. Looking fwd to your big pour! If you tap the mould surfaces with a hammer it will release a lot of those surface bubbles that are attached... If you want to improve the surface finish. Peter

[Ivan_1966]

Hi Peter.
It is very difficult to use paste (non-liquid) in the tight spaces between the bolts. I can only use a brush and a brush. I already primed with PLOPP.
I have no information if it needs to be primed and to dried (as I primed today and will cast the concrete tomorrow). Or tomorrow I have to prime again - fresh ?


About tapping with a hammer.
I am a house builder and have construction equipment. I plan to use a needle vibrator for concrete. But not inside the concrete itself. I rest it on the wooden formwork. But not too much time because the different sizes quartz sand particles will become stratified.

[peteeng]

Hi Ivan - set up is looking great! Many of the concrete grouts say not to vibrate as it will segregate. Plopps fine. Good pouring! A builder making a mill, interesting combo....Peter

[Ivan_1966]

Today me, my son and a friend poured the mold. It was quite heavy. Very difficult material to work with. It looks liquid but is very solid. It's like there's a hard crust on top and it can't be broken through with a putty knife or trowel. The work started well, but after adding the water the cement became heavy, hard, sticky. The double mixer was fixed rigidly to the stand and when the rotary mixer was rotating, the concrete exerted a large lateral force in the direction of rotation. And in the clip I posted in youtube at 4.20 minute, the hard concrete broke the mixer at the base. You can see very little of how the break mixer.. With the gears at the base where the two agitators engage. The clip stops there. I forgot to take pictures of the hand mixer and the broken casing. I'll post pictures tomorrow.

So I had to fight like RAMBO with my other hand mixer. Holding it by the hands inside the rotary mixer.
All ended well in the end. We were able to handle the difficult material. That's it for now.

Video:
https://youtu.be/0gSVNvRaMI8

[peteeng]

Hi Ivan - Thanks for your video, very informative. The grouts I use are very fluid, do you think its the steel fibres that make the final difference in mix stiffness? Peter

[Ivan_1966]

.....do you think its the steel fibres that make the final difference in mix stiffness? Peter

Hi Peter. I don't think so. The percentage is too small for that. I use them rather against the possible appearance of cracks.

Here is the used recipe and the broken hand mixer.

[peteeng]

Hi Ivan - How long are you going to leave it in the mould? We're excited!! Peter

[Ivan_1966]

Minimum 1 month.I can get the top and side shapes out earlier.
But the bottom plate requires lifting the entire form and flipping it 180 degrees. There I think in a month and a half.

[Ivan_1966]

I have edited the video to include the broken mixer and why. It should be known that this arrangement with the stand and the mixer fixed is incorrect and leads to breakage.
This is the new link for the video.

https://youtu.be/3152v44fwt8

[jackjr-123]

Hi Ivan,

Why did you use this UHPC recipe with fibers and shrinkage reducer?

[Ivan_1966]

Hi jackjr-123,
Fibers - mainly to prevent the appearance of microcracks.
Shrinkage reducer - reduce concrete shrinkage to 0.5mm per 1 linear meter.

I quote one of the documents below:

"shrinkage reducing admixtureis recommended in order to minimize
restraint forces during hardening and
alterations in the shape of the finished
construction element."

[jackjr-123]

Thanks. I've seen Durcrete documents, but their recipes are confusing. Sometimes there are fibers and shrinkage reducer, sometimes there are none of them...
I think I remember reading that the fibers are not useful for machine beds, and as you experienced, make the mixing a lot more difficult.

[Ivan_1966]

Yes, the fibers make mixing a lot more difficult. You're right.

But I don't think that they are not useful. For machine beds, they are perhaps superfluous. But I also use them for a gantry.
Check out these documents. The fibers increase tensile strength and compressive strength.

[Ivan_1966]

I continue work on the gantry forms. I have already made all the shapes. I will pour it not straight. Turned 90 degrees, lying on the Y rails.
For maximum flatness (under the Y rails) I use my granite surface plate (which I had bought to work on the parts of this machine).
The surface plate is leveled in a bed of fine quartz sand to level the floor. Due to the insufficient length on the plate I use in addition my two X axis profiles.

[Ivan_1966]

I have a question. I need to replace the balls on the HGR25 carriages for preload ZA.

I'm reading positive reviews about replacing carriage steel balls with Silicon Nitride Ceramic Balls (Si3N4).
Which one is better? Which wears out first if balls are stell.The balls or linear rails. It is preferable - the balls, because they are subject to change.
If they are ceramic - won't the linear rails and the carriage blocks themselves wear out faster in this case?